Data input devices or finger navigation devices, such as computer mice, touch screens, trackballs, scroll wheels and the like, are well known for inputting data into and interfacing with personal computers or workstations. Such devices allow rapid relocation of a cursor on a monitor, and are useful in many text, database and graphical programs. A user controls the cursor, for example, by moving the mouse over a surface to move the cursor in a direction and over distance proportional to the movement of the mouse.
Computer mice, for example, come in both optical and mechanical versions. Mechanical mice typically use a rotating ball to detect motion, and a pair of shaft encoders in contact with the ball to produce a digital signal used by the computer to move the cursor. One problem with mechanical mice is that they are prone to inaccuracy and malfunction after sustained use due to dirt accumulation, etc. In particular, mechanical mice have not demonstrated the accuracy demanded in state-of-the-art mice today, which generally must have a path error of less than 0.5%. In addition, the movement and resultant wear of the mechanical elements, particularly the shaft encoders, necessarily limit the useful life of the device.
One solution to the above problems with mechanical mice has been the development of mice using an optical navigation system. These optical mice have become very popular because they provide a better pointing accuracy and are less susceptible to malfunction due to accumulation of dirt.
The dominant technology used today for optical mice relies on a light emitting diode (LED) illuminating a surface at or near grazing incidence, a two-dimensional CMOS (complimentary metal-oxide-semiconductor) detector which captures the resultant images, and software that correlates successive images to determine the direction, distance and speed the mouse has been moved. This technology provides high accuracy but suffers from a complex design and relatively high image processing requirements.
Another approach uses one-dimensional arrays of photo-sensors or detectors, such as photodiodes (PDs), and a narrowband or coherent light source, such as a Vertical Cavity Surface Emitting Laser (VCSEL). Light from the light source scattered off of an optically rough surface generates a random intensity distribution of light known as speckle. Successive images of the surface are captured by imaging optics, translated onto the photodiodes, and compared to detect movement of the mouse. The photodiodes may be directly wired in groups to facilitate motion detection. This reduces the photodiode requirements, and enables rapid analog processing. The use of a speckle-based pattern has several advantages, including efficient laser-based light generation and high contrast images even under illumination at normal incidence. This allows for a more efficient system and conserves current consumption, which is very important in wireless applications.
Although a significant improvement over prior mechanical mice, these optical navigation system based devices have not been wholly satisfactory for a number of reasons. In particular, VCSELs and PD arrays are typically formed on a substrate or wafer, using semiconductor fabrication or processing techniques. Individual devices, commonly referred to as a chip or die, are then packaged as separate integrated circuits (ICs), which may or may not then be attached or mounted to a common printed circuit board (PCB). Conventional optical navigation systems use external illumination and imaging optics that are not mounted to the IC package or PCB to illuminate a portion of the surface with light from the light source, and to map or image a pattern of the surface to the optical sensor.
One problem encountered with conventional, external optics, is that part they greatly increase the size or footprint of the optical navigation system. Another problem is that the alignment requirements of the optical elements of the illumination and imaging optics to the VCSEL or light source and the PD arrays can be critical to adequate performance of the system. It will further be appreciated that this alignment requirement can greatly impact overall costs and yield of the finished product.
Accordingly, there is a need for an optical navigation system that includes illumination and imaging optics for use in an optical data input devices or finger navigation devices that reduces the overall size and complexity of the system while enhancing system stability and reliability, and substantially reducing costs and increasing yield of the finished device.
The present invention provides a solution to these and other problems, and offers further advantages over conventional optical navigation systems.